Technical Field
The present invention relates to a technique for calibrating a laser scanner.
Background Art
Laser scanners emit laser light on objects to be measured and obtain point cloud position data based on light reflected by the objects. The point cloud position data contains data of three-dimensional coordinates of measured points obtained in dot-like shapes, and a three-dimensional model (for example, a three-dimensional CAD data) of the object can be obtained based on the point cloud position data. For example, when a vehicle, which is equipped with an IMU (Inertial Measurement Unit) and a laser scanner, travels, point cloud position data of the surrounding is obtained by the laser scanner while the location and the attitude of the vehicle are measured by the IMU, whereby a three-dimensional model of the surrounding conditions of the traveled route can be obtained (for example, refer to Japanese Unexamined Patent Application Laid-Open No. 2013-40886).
In the above technique, information (exterior orientation parameters) relating to the position and the attitude of the laser scanner with respect to the IMU must be known in advance. In general, a measuring system is produced by assembling an IMU with a laser scanner therein, in an integrated form, and calibration for determining the exterior orientation parameters of the laser scanner is performed when the measuring system is shipped as a product. Thereafter, the measuring system having the laser scanner that is calibrated is installed in a vehicle.
However, there may be cases in which a user desires to set the laser scanner at a freely selected position in a freely selected attitude when the measuring system is mounted on a vehicle. Moreover, in cases in which the user's vehicle is of a vehicle type or is a vehicle with a structure that is unexpected by the manufacturer of the measuring system, it would be necessary to change the position and the attitude of the laser scanner in accordance with the vehicle.